Modem doesn’t have built in wifi?

@user_af3760 

When you say "doesn’t have built in wifi", do you mean that ethernet connections are working and only wifi doesn't work, or do you mean you don't have any internet access at all?

Either way, the first thing I always do with used equipment is a factory reset.

As per the user manual at https://motorolacable.com/documents/MG7315-UserManual.pdf:

Resetting to Factory Defaults
There may be occasions when you need to reset your cable modem/router to factory
defaults, for example if you have changed the Username and Password and lost the new
values. Note that if you reset your device to its factory defaults, you will lose any
changes you have made to settings in the device.
To reset to factory defaults:
1.) Make sure the cable modem/router is powered on.
2.) Find the reset button on the rear of the unit. It is marked WPS/RESET.
3.) Press and hold the Reset button for at least 10 seconds.
4.) The device will flash its LEDs and commence a reboot sequence.
Note that you will have to manually re-enter any required changes.

I'd give that a try.

HTH

See https://www.xfinity.com/support/articles/xfinity-app-activation .

@user_af3760 

I am confused as to why my modem doesn’t work—it is xfinity approved and worked just fine for the person I just got it from! It definitely has built in wifi. 

it’s a Motorola MG7315

I just signed up for xfinity but I’m already ready to quit it and go back to century link! Can someone help me Figure this out? 

Who is this person you got it from?  A friend?  Someone from online perhaps?

If you can't get that modem activated it may be because it's still on this persons' account.  And also, this modem might be "stolen", meaning it was a rented modem and not a personal modem belonging to the person you bought it from.  You need to call Comcast to find out what is going on with the modem.

I am confused as to why my modem doesn’t work ... Can someone help me Figure this out?

Not without more information, namely, as "Zip" asked, what does "doesn't work" mean exactly? We can't help anyone solve a problem it they haven't told us what the problem is.

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

@user_af3760 

I suspect that just means you can't manage the router functions of your device from the xfinity app or website.

Have you tried managing the router functions of the device as explained in the device's user manual?

HTH

... what I mean is why xfinity is telling me that I need an additional router for wifi ...

Let's ignore that message from the app for the moment. As asked above, do the Ethernet ports work? Does the Wifi work?

Can you log in to the device? The documentation for the gateway says:

If you need to access the MG7315 Configuration Manager, open your Web browser.

Type http://192.168.0.1 in the address bar and press the Enter key.
In the login dialog box, type the following User Name and Password in lower case, then click OK.
    User Name: admin
    Password:   motorola
The status page will appear. If the Status page doesn’t appear, please see the Troubleshooting Tips ...

See https://motorolacable.com/support/MG7315/ for guidance setting the device up.

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

The model you specified is a combination modem and wireless router as you pointed out in the above thread. Did you go through the activation process with the modem? It's not enough to sign up with xfinity and plug a modem in. You need to visit https://xfinity.com/activate and follow the instructions on the site. You will need to install the xfinity app appropriate for your mobile device, sign in, and go through the activation process. Be warned that it might take a number of attempts to activate the modem using the app. It did for me. Contacting support on the phone might be the best route.

Chris